You can use the auto-tagging-override feature to manually set source, medium and campaign using custom values. For example, source/medium can change from dfa/cpm to example.com/newsletter.

If you enable the auto-tagging override feature but do not specify a custom value, then Analytics will apply the default value. For example, if you use a custom value for utm_source, but not for utm_medium, then Analytics applies the default value to utm_medium.

Keep in mind that if you change the source/medium values for Campaign Manager/Display & Video 360 data, then that data may not get automatically classified as Display in your Default Channel Grouping. Under these circumstances, you would have to edit your channel grouping to make sure the data appears in the desired channel.

This override feature applies only to click data, and not to impression data.

The Acquisition > Google Marketing Platform reports (which include the Campaign Manager and Display & Video 360 reports) are not affected by this override feature. These reports use the auto-tagged values.